feat: 添加用户注册功能，包括表单验证和路由注册

backend/docs/swagger.yaml

@@ -685,6 +685,21 @@ definitions:
         description: Order is the created or existing order record (may be nil for
           owner/free-path without order).
     type: object
+  dto.RegisterForm:
+    properties:
+      confirmPassword:
+        description: ConfirmPassword 确认密码；必须与 Password 一致，避免误输入导致无法登录。
+        type: string
+      password:
+        description: Password 明文密码；后端会在创建用户时自动加密（bcrypt）。
+        type: string
+      username:
+        description: Username 用户名；需全局唯一（users.username）；建议仅允许字母/数字/下划线，且长度在合理范围内。
+        type: string
+      verifyCode:
+        description: VerifyCode 验证码（预留字段）；当前版本仅透传/占位，不做后端校验。
+        type: string
+    type: object
   dto.SuperContentItem:
     properties:
       content:
@@ -4208,6 +4223,27 @@ paths:
       summary: 用户登录
       tags:
       - Web
+  /v1/auth/register:
+    post:
+      consumes:
+      - application/json
+      parameters:
+      - description: form
+        in: body
+        name: form
+        required: true
+        schema:
+          $ref: '#/definitions/dto.RegisterForm'
+      produces:
+      - application/json
+      responses:
+        "200":
+          description: 成功
+          schema:
+            $ref: '#/definitions/quyun_v2_app_http_web_dto.LoginResponse'
+      summary: 用户注册
+      tags:
+      - Web
   /v1/auth/token:
     get:
       consumes: